The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
An internal combustion engine (ICE) combusts an air/fuel mixture within cylinders to drive pistons, which produces drive torque. Air flow into an ICE engine may be regulated via a throttle and adjustment in throttle area. Adjustment in throttle area alters air flow into the ICE. As the throttle area increases, the air flow into the engine increases. Fuel injection rate is adjusted in addition to adjustment in air flow to provide the air/fuel mixture. Increasing the amount of air and fuel provided to cylinders of the ICE increases torque output of the ICE. Engine control systems have been developed to control engine torque output.
Spark ignition direct injection (SIDI) refers to direct injection of fuel into cylinders of a spark ignited gasoline engine. SIDI allows for improved control of fuel injection timing. In a SIDI engine, fuel may be injected at various times during a combustion cycle. This is unlike port fuel injected engines where fuel is injected, for example, into a port and/or intake manifold of an engine and before an intake stroke of a corresponding combustion cycle. The increased control that may be associated with an SIDI engine provides increased horsepower, reduced emissions and knock suppression.
Turbo-charged SIDI engines can experience stochastic pre-ignition (SPI) events. SPI events are more likely to occur in turbo-charged engines than non-turbo-charged (or normally aspirated) engines due to the increased pressures, power and torque levels in turbo-charged engines. An SPI event is not controlled by a spark from spark plug at a predetermined engine position (e.g., angular position of a crankshaft of the engine 102). A SPI event may occur due to, for example, a highly pressured air/fuel mixture coming in contact with a highly heated component (e.g., a valve or spark plug) within an engine cylinder. This can occur during high-engine loading (engine loading greater than a predetermined engine load) and at low-engine speeds (engine speeds less than a predetermined engine speed). An SPI event progressively degenerates due to the early ignition associated with the SPI event and since components within an engine cylinder tend to increase in temperature with each engine cycle during the SPI event. For this reason, a SPI event may be referred to as a run-away pre-ignition event.
SPI events tend to occur randomly and sporadically and can thus be unpredictable. SPI events can negatively affect fuel economy and/or control of torque output of an engine. If not minimized and/or prevented, SPI events can cause damage to engine components over time.